A unifying goal for this research is to understand the mechanisms of fragmentations so that interpretations of production-ion spectra can be placed on a firm foundation. Therefore, the first aim is to evaluate various spectrometry methods to distinguish isomeric adducts and potential biomarkers. New to our effort will be a major activity to understand isomerically distinct fragmentations by using molecular orbital calculations. Six classes of fragmentations are identified for study on the basis of our experience in this area. In parallel with developing an understanding of ion chemistry, we will develop and validate electrospray liquid chromatography (LC/MS) and LC-tandem-MS methods for the trace determination of estrogen metabolites, conjugates, and nucleobase adducts. We are proposing two approaches: a low-throughput method that posses maximal certainty for identification of analytes and a high- throughput method for rapid screening of tissues. These methods will then be used to support research in other subprojects. Emphasis will be on analysis of tissues for estrogen biomarkers and on biological fluids for polycyclic aromatic hydrocarbon (PAH) adducts. We will also emphasize a biophysical aspect of MS in which the instrumentation is used to evaluate the binding of carcinogens to DNA by investigating non- covalent complexes of small duplex oligodeoxynucleotides and estrogens or PAH. Following the study of interactions, we focus on the modification reactions themselves by devising and utilizing MS methods for following directly the reactions of carcinogens with model single and double-stranded oligonucleotides. Sufficient preliminary results support the launch of these latter, relatively new projects.